RXRβ Antibody #8715

The human retinoid X receptors (RXRs) are encoded by three distinct genes (RXRα, RXRβ, and RXRγ) and bind selectively and with high affinity to the vitamin A derivative, 9-cis-retinoic acid. RXRs are type-II nuclear hormone receptors that are largely localized to the nuclear compartment independent of ligand binding. Nuclear RXRs form heterodimers with nuclear hormone receptor subfamily 1 proteins, including thyroid hormone receptor, retinoic acid receptors, vitamin D receptor, peroxisome proliferator-activated receptors, liver X receptors, and farnesoid X receptor (1). Since RXRs heterodimerize with multiple nuclear hormone receptors, they play a central role in transcriptional control of numerous hormonal signaling pathways by binding to cis-acting response elements in the promoter/enhancer region of target genes (2).
RXRβ, like other members of the RXR subfamily, possesses a characteristic tripartite modular structure consisting of (a) a highly conserved central region containing the C₄/C₅ zinc-finger domain, which is responsible for DNA binding; (b) a relatively well-conserved C-terminal region, which contains the hormone binding and dimerization domains; and (c) a variable N-terminal domain, which has been implicated in either transactivation or repression of target genes (2). Variability within the N-terminal domain is thought to be the result of alternative splicing and/or differential promoter usage (3-5). The murine RXRβ was initially identified because of its ability to bind to the regulatory region II in the murine major histocompatability complex (MHC) class I promoter and is therefore also referred to as H-2RIIBP (6). Genetic ablation of murine Rxrb produced approximately 50% lethality in utero and males that survived had defects of spermatazoa, which resulted in sterility (7). Further studies revealed that expression of a Rxrb mutant with an impaired AF-2 core led to abnormal lipid metabolism in Sertoli cells, suggesting functional interactions between Rxrb and other nuclear receptors that control lipid metabolism (8).